1. Field of the Invention
The invention relates to a grommet configured to fit on a wire harness routed in a motor vehicle and to be mounted in a through hole of a vehicle body panel to prevent entry of water, dust, and noise into a vehicle passenger compartment from the outside of the passenger compartment.
2. Description of the Related Art
A grommet for a wire harness is formed of rubber or elastomer, and includes a small-diameter tube and a large-diameter tube. The small-diameter tube is configured so that a wire group that constitutes the wire harness can be fit tightly therein. The large-diameter tube increases in diameter continuously from an outer periphery of the small-diameter tube and has outer peripheral surface with an annular vehicle body locking depression. The small-diameter tube of the grommet is expanded with an expanding jig so that the wire harness can be inserted therein. An adhesive tape then is wound from a distal end of the small-diameter tube of the grommet to an outer peripheral surface of the wire harness to fix the grommet to a predetermined position on the wire harness.
The inventor of the present application has proposed using a binding band 100 instead of adhesive tape to fix a grommet 101 to a wire harness 102, as shown in FIG. 7 herein and as described in JP-A-2005-65354.
FIG. 8 shows a recent pipe harness 110 for a hybrid motor vehicle or an electric motor vehicle. The pipe harness 110 includes a wire harness 102 that is passed through a metallic pipe 111 and a grommet 120 that is fit on the pipe 111. The pipe harness 110 is routed under a floor of the vehicle, and the grommet 120 is fit into a through hole in a floor panel, as shown in FIG. 8. A resin binding band 130 is wound around a small-diameter tube 121 of the grommet 120 to fasten the small-diameter tube 121 tightly on an outer peripheral surface of the pipe 111.
More specifically, two annular ribs 122A and 122B project out on an outer peripheral surface of a distal end of the small-diameter tube 121 of the grommet 120, and a band winding portion 124 is defined between the ribs 122A and 122B. A band 131 of the binding band 130 is wound on the winding portion 124 and is drawn through a main body 133 and pulled to lock a locking strip of the main body 133 in a locking groove of the band 131.
The grommet is molded of a resilient material and is thin to be brought into tight contact with the outer peripheral surface of the pipe 111 on the outer periphery of the wire harness. In contrast, the binding band 130 is a molded resin. Thus, if the band 131 is pulled strongly when fastening, the metal pipe 111 is subject to slippage. Therefore, as shown in FIG. 8(B), a gap G tends to be formed between the small-diameter tube 121 and the pipe 111 as the band 131 pulls the winding portion 124 of the small-diameter tube 121 of the grommet. Water can enter through the gap G from the underfloor and into the passenger compartment.
An annular sealing lip 125 has been provided on an inner periphery of the band winding portion 124 of the small-diameter tube 121 of the grommet 120, as shown in FIG. 8(C), to avoid forming the gap G. However, the sealing lip 125 also is pulled when the band winding portion 124 is pulled by the band 131, and hence the gap G is not eliminated completely.
The gap between an inner periphery of the band winding portion 124 and the outer peripheral surface of the pipe 111 can be prevented by setting the inner diameter of the small-diameter tube 121 equal to the outer diameter of the pipe 111, as shown in FIG. 8(D). However, when the inner diameter of the small-diameter tube 121 of the grommet equals the outer diameter of the pipe 111, an inner peripheral surface of the small-diameter tube 121 sticks to the outer peripheral surface of the pipe 111 as the pipe 111 is being fed through the small-diameter tube 121 of the grommet, which hinders a smooth through-feed operation. Therefore, a lubricating agent 140 must be filled between the pipe 111 and the small-diameter tube 121. However, the lubricating agent 140 can cause the pipe 111 to slip when the band 131 of the binding band 130 is wound around the outer peripheral surface of the small-diameter tube 121. Hence the small-diameter tube 121 cannot be fixed adequately at a predetermined position on the pipe 111 even when the band 131 is fastened.
In view of the above-described problems, it is an object of the invention to provide a grommet that enables a metal pipe of a pipe harness to be inserted easily through the small diameter tube of the grommet without using a lubricating agent, while also achieving a tight contact. It is also an object of the invention to prevent slippage between the pipe and the small-diameter tube and to prevent formation of a gap that could cause entry of water when fastening the small-diameter tube of the grommet on the pipe with a binding band.